1. Field of the Invention
The invention generally relates to a process and apparatus for recovering energy, in the form of electrical power, from an engine on a test bench, and more particularly from thermal vehicular engines.
2. Description of the Prior Art
It is necessary to perform measurements on engines at the factory in order to test their operation and/or endurance.
These factory tests, to be representative of the operational conditions experienced during use, must be performed under varying speed and torque conditions. Generally, the braking torque used to perform these tests is obtained, for example, by means of a friction brake, by a "Froude" water brake or by an electromagnetic Foucault current brake.
The energy furnished by the engine during the test is measured, the measured energy corresponding to the approximate efficiency of the engine. The energy expended is, generally, removed by the circulation of cooling water in the brake and, as a result, is lost.
Thus, a considerable amount of energy is wasted, and it is for this reason that it is desirable to recover at least a portion of this energy.
However, it is particularly difficult to reuse the recovered energy on location, for example in the form of heat, and therefore, it has become apparent that a particularly desirable manner of recovering this energy resided in its transformation into electric energy in a manner so as to be able to reinject it directly into the electrical network of the factory.
There presently exists a certain number of techniques directed to the transformation of the mechanical power of a variable velocity engine into a fixed frequency electrical power.
The known techniques include hydraulic apparatus having hydrostatic transmissions, and mechanical velocity adjusters, or slip clutches, which are adapted to turn an asychronous generator connected to an electrical network.
There also exists entirely electric apparatus such as the Ward Leonard system or others provided, for example, with a generator and an inverter, or with an alternator, with a rectifier and with an inverter, or with an asychronous or synchronous motor, with a rectifier and with an inverter.
However, a system of the Ward Leonard type is a costly system comprising two continuous-current machines whose maintenance is difficult and which require connection to an asychronous generator which feeds the network. The above-noted apparatus is provided with inverters generally having thyristors, which produce strong harmonics causing undesirable disturbances to the network into which the current is reinjected.